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 under the collar bones, near the neck. The one that empties under the left collar bone (3, Fig. 66) is called the thoracic duct because it goes up through the thorax just in front of the spinal column (1, Fig. 66). The other at the right side of the neck is called the right lymphatic duct (see Figs. 64, 65).

In persons with the dropsy, the lymph accumulates in the lymph spaces and is not drained away by the lymph flow. Dropsy usually shows itself first by swelling of the feet and the leg below the knee. (Why? See Exp. 2.)

There is a set of lymphatics called lacteals, situated in the abdomen, which have the function of absorbing digested fats from the intestine (Figs. 66, 100, and colored figure 2).

What makes the Lymph Flow?—The heart does not, for its pressure is not transmitted beyond the blood tubes. The successive pressures of a working muscle move the lymph forward in the lymphatics in the same way that the blood is moved forward in the veins, and the valves keep it from moving back. When riding a trotting horse, or in a jolting vehicle, the lymph is moved beyond the valves at every jolt (Fig. 64). Without exercise the lymph stagnates, and the body becomes poisoned by its own wastes. At every expansion of the lungs lymph is drawn into the chest; and it is forced out of the chest at every contraction. Deep breathing is as great a benefit to the body in moving stagnant lymph as it is in purifying the blood.